Preheat the oven to 350° and lightly oil a 9x13" baking dish.
Pour the prepared peaches and cinnamon, if using, into the pan and evenly spread.
In a bowl, combine the remaining ingredients until a crumbly dough forms.
Pour the dough-crumbles over the peaches and cover evenly.
Bake in preheated oven for 45 minutes, or until peaches are bubble and topping begins to lightly brown.
Let cool slightly and serve on its own or with ice cream or whipped topping.